The result is an inverse for a relative to the tensordot operation
tensordot(a,b,ind), i. e., up to floating-point accuracy,
tensordot(tensorinv(a),a,ind) is the “identity” tensor for the
tensordot operation.

Parameters:

a:array_like

Tensor to ‘invert’. Its shape must be ‘square’, i. e.,
prod(a.shape[:ind])==prod(a.shape[ind:]).

ind:int, optional

Number of first indices that are involved in the inverse sum.
Must be a positive integer, default is 2.